Radiant-energy signal direction finder



oct. 21, 1947. I BAD, 0UGH L|N 2,429,519

RADIANT-ENERGY SIGNAL DIRECTION FINDER INVENTOR BERNARD D :LOUGHLIN Oct. 21, 1947. B D, 'LOUGHUN 2,429,519

RADIANT-ENERGY SIGNAL DIRECTION FINDER Filed Sept. 20, 1943 ,4V`Sheets-Sheet 4 INVENTOR BERNARD D. LOUGHLIN Patented Oct. 21, 1947 EADIANT-ENERGY SIGNAL DIRECTION FINDER Bernard D. Loughlin, Bayside, N. Y., assignor, by mesne assignments, to Hazeltine Research, Inc., Chicago, Ill., a corporation of Illinois Application September 20, 1943, Serial No. 503,069

(Cl. Z50-11) 19 Claims. 'l

The present invention pertains to a direction finder for determining the direction of reception, or bearing, oi a particular radiant-energy signal.

Many prior art arrangements have been proposed for determining the direction of reception of a radiant-energy signal. One such prior art arrangement is described in copending application, Serial No. 423,514, led December 18, 1941, now Patent No. 2,407,281 issued Sept. 10, 1946, in the name of J. Kelly Johnson et al. and assigned to the same assignee as the present invention. The direction finder there disclosed comprises a receiving pick-up system having a directive pattern, means for controlling the pick-up system to cause the directive pattern to rotate, a line-tracing device, and means for synchronizing the line-tracing device with the rotation of the directive pattern. The arrangement further comprises means responsive to the amplitude of a signal received by the pick-up system for shifting the line traced by the line-tracing device in accordance with the directive pattern, and means for cyclically displacing the line traced by the line-tracing device at a frequency which is high with reference to the frequency at which the directive pattern is rotated, thereby to trace intersecting lines `sharply indicative of the directio-n of reception of the received signal.

.IngeneraL` the operation of the described arrangement` is entirely satisfactory when only a few signals are received during a S60-degree rotation of the antenna directive pattern. However, when several signals are received during such rotation, the .direction-iinder pattern produced by the line-tracing device may be complex and it may be .difficult to obtain accurate bearing indications yof any particular one of the received signais. yThe present invention constitutes an improvement .on the above-mentioned copending application of J. Kelly Johnson et al.

It is, therefore, an object of the invention to provide an improved .direction finder for determining the direction of .reception of a radiantenergy signal which substantially avoids the above-mentioned limitation of the described prior art arrangement.

It is another-object of the invention to provide `an improved direction nder including a pick-up system having a directive pattern which is 2 iinder for determining the direction of reception of a particular radiant-energy signal comprises a pick-up system having a directive pattern and means for controlling the pick-up system to cause the directive pattern to rotate through a predetermined azimuth. The direction finder also includes line-tracing means and means for controlling the line-tracing means to trace a line at a frequency which is related to the frequency of rotation of the directive pattern by an integer greater than unity. Additionally, there is included in the direction iinder means responsive only to the amplitude of signals picked up within a predetermined fractional portion of the directive pattern azimuthal rotation for shifting the line traced by the line-tracing means in accord- .ance therewith to trace at least a portion of the directive pattern.

A direction finder in accordance with the invention includes a pick-up, or antenna, system having a directive pattern. The antenna system is rotated, thereby to cause its directive pattern to rotate through an azimuth of 360 degrees. The direction finder also includes a line-tracing arrangement from which bearing indications are obtained comprising a pair of cathode-ray devices. The cathode-ray beam of the rst device is controlled to trace a circular path in synchronism with the rotation of the directive pattern. The beam of the second device is controlled to trace a circular path at a frequency related to the frequency of rotation of the directive pattern by an integer greater than unity, this integer being 4 in a preferred embodiment. The radius of the circular path traced by the iirst device is modulated in accordance with the amplitudes of all signals picked up during the directive pattern rotation and thus the iirst device traces the directive pattern with reference to the direction of reception of each received signal. However, the radius of the circular path traced Vby the second device is modulated only in response to the amplitude of a particular signal picked up within a predetermined fractional portion of such azimuthal rotation, for example degrees, so that this second device traces the directive pattern with reference to such particular received signal. While the beam of the second device is tracing the directive pattern, it is periodically displaced at a high frequency to produce intersecting directive patterns. The intersections of these patterns, with reference to scale divisions representing diierent predetermined positions of the antenna, accurately determine the bearing of the particular signal` Furthen, that portion of the the names of Bernard` D. Loughlin et al., now

Patent 14045238, issued July 16, 1946, and assigned to-theisame assignee as the present application. More specifically, each device 361, 3l, represented schematically inthe drawings, comprises relatively.l movable primary. and. secondary ele-` ments, the relativevposition of lwhich determinesv the electrical;` coupling therebetween.` The primary. elements are xed orv stationary andarevr thus effectively mechanically coupled to the supporting structure (not shown) of antenna system ;,212. The secondary elements are arranged for rotation within their associated primary elements, being mechanically coupled with antenna system 20, 2| for rotation in synohronism therewith, asindicated by broken line 2 4".

Oscillation generators and 36 supply oscillations of a frequency much greater than the maximum frequency of rotation of antenna system 2-8, `2:| Inductive-coupling devices 3B andl are utilized to vary the operating frequencies of oscillators 35i and 35, respectively, in accordance with the rotation of' antenna system 2B, 2l. This may be accomplished in any well-known manner as, for example, by individually including one such: coupling device in a quadrature-phase voltagefeed-back circuit of one ofthe oscillators, as-` disclosed in the Loughlin. et al. application` referred to above. The described means produce two` frequency-modulated control signals', one having a mean carrier frequency f1 corresponding tothe nominal operating frequency of oscillation generator 35' and the other having a mean carrier frequency f2 corresponding to the nominalI operating frequency of oscillation generator 3:5.. These control signals are utilized in means included in the remoteline-tracing arrangement, to; be described hereinafter, for controllingthe beam deection ofline-tracing device 51.

The means included in signal generator Mi for controlling line-tracing device 63 is substantially the same as that justdescribed. This means, in. the illustrated embodiment, comprises additional1 inductive-coupling devicesli and 3 l electrically coupled with additional oscillation generatorss` andV 36! and` mechanically coupled with antenna system 2.0, 2l. Howeverthe secondary elements of devices 39', 3l" aremechanically coupled with antenna system 20, 2| through such a speedchanging device that the secondary elements thereof are driven at four times the speed of the antenna system. This coupling arrangement includes a gear train 32 33, gear 32 being rotated with the antenna system as4 indicated by. broken, line24, and gear Sii-being coupled to the secondary elements of devices 3B', 3l', as indicated by broken line 34. The means under consideration produce additional frequency-modulated control; signals having mean carrier frequencies f3 and f4. which correspond, respectively, to the nominal operating frequencies ot oscillation generatorsl' and 3B', These signals are suitable for controlling the beam of line-tracing'device 6310i Fig; 2;

Signal generator 43. also` includes means for producing scale divisions onA the screen off linetracing device 631, which divisions individually correspondv to diierent predetermined positions ci antenna systemf20,-,2:land facilitate obtainingbearing` indications from; the direction: finder. Such meansgcomprise a phasefmodulator 31 me-` chanically coupled with antenna system 20, 2| and;V electrically,` coupled: with an oscillation generator 40. The design of modulator 31 and its coupling: arrangements` may be generally similarl tothe phase modulator` included in the marker. system: forming1-the-subject matter of copending` application- Serial' Noly 503,070; filedi concurrently.A lielewithrin thename of Bernard D. Loughlin, andfassigned to the same, assigneeas the present invention. In particular, modulator 31, which'- isp represented, schematically,` consists` of aninductiyercoupling device havin-g: a pair of primary` elements:` positioned in; mutually perpendicular.- planes anda` secondary element inductively cou-l pledito and umounted forrotation within suchprimary elements;` While` the primary elements are. xed-orf stationaryg, the-secondary element is mechanically-coupledwith antenna system 20, 2t; for.' rotation therewith through a mechanical couplingfarrangement including a geartrain 32, 38;? andE an suitable'` driving shaft indicated by brokenfline 39=. Thegeart-rainis selected to drivethe secondary element; at twelve times thef f-requency' of antenna: rot-ation;

The primary' elements of modulator 31' are-so electrically coupledrwithoscillat-or Ml` as to be eX- cited;` in; phase l quadrature. Oscillation genera-- tor. dik supplies `a carrier `'signal which comprises referencey oscillations; having: a sinusoidal wave form and a frequencygffo; much greater than the maximum yfreoluencyof "rotation of the secondary elementoi device 31. A'phase-modulated carrier signal is obtainedfrommodulator 31, being-takendirect-ly4 from its secondary element. This output*` signal comprisesoscillations, hereinafter, referred; to as comparative oscillations, which are induced in the` secondary element in response to` the, excitation of theA primary elements. The comparative oscillations obtained from modulator 3'1" are utilized in means, described hereinafter, included in' the remote line-tracing ar- A rangement for deriving marker signals which produce the desired scale divisions.

In deriving the marker signals in the receiver` of lig.` 2, it is, preferredto compare the relative phase ofthe comparative oscillations from phase modulator 3'1 with the reference oscillations produced'in oscillation generator 40'. For this purposeiit is. expedient to include in signal generator 46; an arrangement for producing reference-signal components suitable for providing a phasereference signal to be utilized in making such a phase comparison at the remote line-tracing arrangement. The reference-signal components are developed in a balanced amplitude modulator IH having one input circuit coupled to oscillation generator 451 and another input circuit coupledto a further oscillation generator 42 which supplies an. amplitude-modulating signal having a frequency f5, defined more particularly hereinafter. The output' circuit of modulator l is designed to select only the upper and the lower sidebands ofA amplitude modulation. The developed` modulation components have predetermined'phase relations with reference to the carrier` signal from oscillator 40 and hence are suitable phase-reference signal components.

An additional amplitude modulator 43' is included' in. the arrangement under consideration, having input circuits individually coupled to thel output circuit of; balanced modulator 4I and direction-nder receiver 25. Modulator 4 3 pro- 7. vides means for amplitude-modulating the phase-reference signal components in accordance with the output signal of receiver 25 so that the output signal of this receiver may be conveniently translated to the remote line-tracing arrangement. It is preferred that units 40-43, inclusive, be generally similar to the arrangement for translating phase-reference signal components described in copending application Serial No. 503,071, led concurrently herewith in the name of Bernard D. Loughlin, now Patent 2,403,385, issued July 16, 1946, and assigned to the same assignee as the present invention.

The output circuits of units 35, 35', 36, 36', 31 and 4 3 are coupled to the input circuit of a combining amplifier 44. The output circuit of amplifier 44 connects with input terminals 45, 45 of signal-translating channel 41 for applying the signals amplified therein to channel 41.

Referring now more particularly to Fig. 2, the line-tracing arrangement comprises the pair of cathode-ray tubes 51 and 63 previously mentioned.Y While these tubes are of conventional construction, having screen surfaces perpendicular to their longitudinal axes, their representation is distorted in the drawing in order that the screens may appear more clearly. The arrangement also comprises'an amplifier and equalizer 5| coupled to output terminals 50, 50 of the signal-translating channel for selectively amplifying the components of the received signal to compensate for any nonuniform frequency-response characteristics of the channel.

As previously indicated, means are provided for utilizing certain of the received control signals to cause the line-tracing means to trace a first line in synchronism with the rotation of the antenna directive pattern. This means consists of horizontal and vertical deflection channels associated, respectively, with the horizontal and vertical deiiecting elements of tube 51. The horizontal channel includes a lter 52 coupled to the output circuit of unit 5| and having connected in"v cascade therewith a limiter 53, an amplitude modulator 54, a frequency-modulation detector 55, and a horizontal-deflection amplifier 55. Similarly, the vertical channel is comprised of a filter 58 coupled to the output circuit of unit 5| and having connected in cascade therewith a limiter 59,' an amplitude modulator 5|), a frequency-modulation detector 6|, and a verticaldeilection amplifier 62. Filters 52 and 58 are individually designed to select received frequencymodulated control signals having the carrier frequencies f1 and f2, respectively.

While the elements of the described deflection channels may be of any well-known design and construction, a preferred circuit arrangement for detectors 55 and 6| is illustrated in Fig. 3. As shown, each such detector comprises a pair of diode rectiers |0|, |02 coupled, respectively, to tuned circuits |03, |04 of a discriminator network to which al frequency-modulated signal may be applied by way of an inductively-coupled tuned circuit |05. Preferably, circuits |03 and |04 are tuned to frequencies equally displaced above and below the mean carrier frequencyof the applied signal. Output circuits |01 and |03 are provided for rectiers |01 and |02, respectively, and a voltage divider including resistors V|09 and |||l coupled to the output circuits and having a groundedA common terminal permit output voltages of opposite polarity to be obtained at terminals a and b. The detector is arranged to provide output unidirectional signals of opposite polarities for a purpose to be described hereinafter.

Also, as previously indicated, the arrangement of Fig. 2 includes means for utilizing certain others of the control signals for causing the linetracing means to trace a second line at a frequency which is related to the frequency of rotation of the antenna directive pattern by an integer greater than unity. Such means comprise horizontal and vertical deection channels coupled, respectively, with the horizontal and vertical deflecting elements of tube 63. The horizontal channel is provided by units 52-56 connected in cascade and individually corresponding to units 52-5, respectively. Similarly, the vertical channel is provided by units 58'-62' which individually correspond to units 53-62, respectively. Filters 52' and 58' are individuallydesigned to select the frequency modulated control signals having carrier frequencies f3 and f4, respectively, for utilization in the deflection channels associated with tube 63.

The received phase-modulated carrier signal and reference-signal components are utilized in an arrangement included in the line-tracing means for deriving the aforementioned marker signals. Except for the design of the phasemodulation detector, this arrangement is generally similar to the receiver portion of the phasemodulation system described in copending application Serial No. 503,071 of Bernard D. Loughlin, now Patent 2,403,385, issued July 16, 1946, referred to above. As illustrated, this arrangement includes nlters 54, 65 and 56 connected with the ampliiier and equalizer 5| for individually separating the phase-modulated carrier signal and each of the above-mentioned reference-signal components. Filters 64 and 65 are designed to have pass bands with mean frequencies corresponding to individual ones of the reference-signal components and sufficiently wide to pass the band of amplitude-modulation components associated with each such reference-signal component. The pass Yband of filter 60 has a mean frequency corresponding to 'that of the carrier component of the phase-modulated signal and is sufficiently wide to pass the band of modulation components associated therewith. A modulator or mixer 61 is coupled to the output circuits of lters 54 and 65 for the purpose of effectively combining the separated reference-signal components. The output circuit of mixer 51 is designed to select the upper side-band modulation component which comprises a phase-reference carrier harmonically related to the carrier signal generated in oscillation generator 40 of signal generator 46 (Fig. 1) and, thus, also harmonically related to the carrier component of the received phase-modulated carrier signal. A frequency converter or multiplier 08 coupled to the output circuit of lter 05 is provided for doubling the frequency of the received phase-modulated carrier signal to facilitate comparing the phasereference carrier signal obtained in mixer 51 therewith. The signal outputs of units 51 and 68 are utilized in a phase-modulation detector, indicated generally as 95, having input circuits individually coupled thereto.

It is preferred that phase-modulation detector be similar to detector arrangement 11 of the above-mentioned Loughlin application Serial No. 503,070. Such construction is illustrated in the drawings where detector 95 is represented as comprising apulse detector 69 having one input circuit coupled 4to mixer 6'.' and a second input cir- T9 'cuit `coupledto frequency multipliers 68. Freguency multiplier 12 and :13 are includedin detector arrangement .35,beingcoupled in cascadeto mtheoutput circuit of ,mixer 6.1 for the purposeof limultiplying Vthe .frequency of lthe signal output thereof successivelyyby ,the factors 3 and 5,r e lspectively. .Additional frequencymulti-pliers '1 -2 -and..113,are.included in arrangement 9 5 and are rcoupled ingcascade to :theoutput `circuit of mulvmodulating theirequency-modulatedcontrol sig'- nals translated in thesechannels.

rnfaccnrateindication of the bearing of a parjticular radi ant.energy signalis obtained in the dxrectiongnderbytracing Von Vthe screen tube `6 3 at Jleas t apart oithe antenna directive pattern .With-reerence to the vdirection of reception of s uohparticular signal. -flhis isachieved through means responsive only to the amplitude of sig- -tiplierili .for similarly multiplying the frequency 10 nais-pickedup Within ja predetermined fraCtOnal -offthesignaloutput thereof. ;Furthenarrlgement toiincludesipulse detectorsll! andl. Detector 10. hasI one input circuit coupled to frequencymultiplier :68 and another input circuit coupled .t0 :frecuencymultiplierilWhile the inputcreuits ,of

rdetector 11| are individually coupled to .frequency in accordance therewith to Aproduce major scale idivisions-and asecond means which isresponsive tto a seoondsuccession-,of marker signals for modoulating `the intensity;ofthe beam in accordance therewith toproduceminor scale divisions.

The rst aforesaid means includes amodulator ..14 having one `input :circuit toWhiCh high-frefguency oscillations aresuppled from an oscillator 15 `and ar second input circuitto which a rstsuc- .cession of marker .signals `is applied, this suc-.

ecession ofsignalsfcomprisingmhecombined signal .outputsof pulse detectorssand 1li. The oscilla tions from oscillator 15 have a'frequenc'y which ishigh With-.referenceto the repetition frequency .offt he markersignals .appliedto modulator 14..

The signaloutput of modulator 14.is applied to a y.voltage amplifier ,16 through which the second anodeyoltage is supplied to tube .63 from a highvoltage powersupply .11. `Themeans for modulating the intensity of the beam of tube,.63 to providevfminorscale divisions comprises the control relectrode ofthe tube to ...whicha secondsucoession o imarker signals is applied. This succession of signals is obtained .dierectly from the output circuitof pulse detector H l and is applied to the control electrode by Way of a keying amplifier ,18 and vampliiier 19.

, Inorder ,to obtain bearing indications fromthe direction nder, the linetracing arrangement also includesmeans responsive to theamplitudes of signals `picked upduring the rotation of the an- L"'Ihese modulation components represent the am-..70

'plitude variations of` signals picked up during the `rotation Aof antenna'system 20,21 andare sup- `plied to modulators-54` and B-(lincluded in the horizontal and vertical Vdeflection channels, respec- Y tively, vof tube A15"! 'for `the-purpose of arnplitude--l portion of y the antenna system azimuthal rotation for shifting the second line traced ,by the line-tracirig means. In particular, this means shiftsltheline.tracedflbythe beam of cathode-ray tubeisandcornprises .additional detectors `3 l, 8.2 Vivvhich are-iridividuallycoupled to ltersll and. 65, respectively, anda control arrangement described hereinafter.

Detectorsf8l .and 8 2.may.be .identical in conistruction,and arearrangedtoprovide an output @signal of. controllable amplitude. A preferred circ uit.. arrangement'. therefor ,is ,illustrated in Fig. 14 .whereit willbeseen vthateach detector includes a diode rectifier l l5 to whichan,,amplitude-modulated signalmay be applied .by .way of a transformer .l L6, l.1, the primary winding H B thereof being coupled with .the ,iilter 6 4. or 5 5 associated with the .particular detector. The load circuit of the ,.detectorincludes aresistor H B bypassed A by-e.. condenser i. l 9 in 4conventional manner. A Arepeater 20, c oup1cd to the load circuit of recer l5 .translates an. output signal ,therefrom to 'anltputterminal c provided for the detector Qariangernent. Repeater I,2 D i s normally blocked to, its cathode through aresistor l2 I coupled tothe .space.current.supply,.indicated -l-jB, of the repeater. The outnutterminal C, beine coupledfto .-.e Cathodedpad ,1.2.2. 0f the repeater. produces ,an

0 .4 outputsignal ofjthesame polarityas that applied itojtheinputcircuit.

The amplitude of the output signals obtained at terminal c is controllable through a circuit arrangement which applies V.a control elect of positive polarity andY adjustable magnitudeto the controheiectrode ofrepeater 12.0. As shown, this circnuit arrangement includes a Voltage-divider resistor L23 connectedin circuit with a suitable of undreCticmeil potential, indicated +B Vacuum. tube i? llis anelectronic devicein shunt relation with resistor 12.3 for effectively shorteircuiting the resistor, thereby to remove :the r 0911131701.potential supplied from resistor |23 to thecircuitof repeater 120. 'Vacuum tube +24 is normally'biased to cutoi but may be rendered conductive f or the purpose of Ashort-circuiting `resistor "1;23 :in responseto a control potential applied .to .its .input `terxrlinal d from a further -Controlarrenifement presently t0r bedeserbed -The control arrangement of'Fig. 2 which derivesacentroleleetferapplication t0 terminals@ ...ofthe aferedesclibed .deteetorseemprises a bleekout Qontrol jl `square-wave limiter 92. The .'bglccirreuteentroiis. a .manually adjustable Switch having rieur .terminals .individually .Coupled t0 `output terminals@ and b ,of detectors A55 andjl .included inthedefleetien channels of tube l51- In the -illustrated embodiment, the .Switch has a rsingle blade or. switcharm1lj25 adapted selectively to engage one of4 the four input terminals. Switch arm.iziscoupledto theinput circuitof squarewave limiter 92 T forsupplying thereto the signal .y obtained at -tl'1e seleoted. inputA terminal. .UnitlBZ may comprise anyocnventional amplier ar- :Iarlgement .adjusted rior symmetrically limiting directive pattern. This `means, comprising unit 83, which derives a conil an applied signal, thereby to shape the signal into one having a substantially rectangular wave form. For example, the arrangement may be as indicated at i in United States Letters Patent No. 2,271,203, granted to Jasper J. Okrent on f January 27, 1942. The ksignal of rectangular wave form obtained in square-wave limiter 92 is applied to terminals d of each detector 8|, 82 for selectively causing each such detector to respond only to the amplitude of signals picked up within a predetermined fractional portion of the rotation of antenna system 20, 2 I.

rllhe signal outputs obtained from detectors 8| and 82 under the control of the described control arrangement are combined and supplied to the input circuit of an additional square-wave limiter 83 where the applied signal is formed into a control pulse of substantially rectangular wave form. The limiter includes conventional circuit arrangements for applying the developed control pulse with opposite polarity to a pair of output terminals e and g hereinafter referred to, respectively, as the positive-pulse terminal and the negative-pulse terminal.

The control pulses developed in unit S3 perform several control functions in connection with the line-tracing arrangement under consideration.

`For example, these pulses control the application of the signal outputs Vof detectors 8|, 82 to modulators 5LB', Se included in the deflection channels of tube |53. To this end, the positive-pulse terminal of unit 83 is coupled to a keying amplifier 84 which delivers the combined signal output of units 8|, t2 to modulators 54' and B0. The keying amplier may be a conventional amplier biased to cutoff in the absence of an applied control pulse of positive polarity. Modulators 54 and til' amplitude-modulate the frequency-modulated signals translated through the horizontal and vertical deflection channels, respectively, of tube 63 in accordance with the output signals of detectors 8|, 82.

' A voltage supply 91 is also coupled to the positive-pulse Aterminal of unit 83 for applying a unidirectional potential of predetermined magnitude to modulators 54 and 60 only during intervals when there is no signal output derived in the circuits of detectors 8| and 82. This arrangement may be similar to that shown in Fig. 4, comprising a voltage divider |23 from which the unidirectional potential is derived and a control tube |24 for effectively suppressing this potential when an output signal from detectors. 8| and 82 causes a control pulse to be applied to unit 9'! from square-wave limiter 83.

In order to produce clear direction-finder patterns on the screen of tube 63, it is desirable to disable the described marker system during intervals when the beam of this tube is tracing a is accomplished by trol effect from the direction-finder signal output of detectors 8|, 82, as hereinbefore described.

YThis meansralso comprises oscillation generator 'l5 coupled to the negative-pulse terminal of unitY 33 and keying amplifier 18 similarly coupled to unit 83, each of which lis rendered inoperative in response to the control effect provided by unit 83.

There is also associated with tube E3 an arrangement for producing a pair of overlapping `direction-Hinder patterns the intersections of which with reference to the scale divisions providedyon the screen thereof sharply indicate the 'tracedby the beam' of tubeASSata frequency which'is high with' reference ".to the' frequency at which the line is traced. This means is, preferably, generally similar to the line-displacing arrangement particularly described n copending application Serial No. 503,073, filed concurrently herewith in the name of Jamesv F. Craib and assigned to the same-assignee as the present invention. In the drawings, the arrangement is indicated as 81 and comprises a rst winding disposed about the neck -portion of tube 63 for cyclically displacing the beam thereof. This winding is excited by a high-frequency sine-wave oscillation generator 88 through a power amplifier 89. A second winding is included' in unit 81, being inductively coupled to the rst winding thereof to supply induced oscillations to Ya full-wave rectifier and limiter 6, as indicated by connection 90. Unit 96, through rectification of these oscillations, produces a positive controlvoltage comprising pulses having a frequency twice that of the rectified oscillations. This control voltage is applied through amplifier 'i9 to the control electrode of tube 63. Additionally, oscillation generator 88 is coupled to the positive-pulse terminal of unit 83 to provide means for energizing the described beam-displacing arrangement only during intervals when the beam of tube 63 is controlled to trace a direction-iinder pattern.

There is also included in the arrangement ofl Fig. 2 a pair of transient block-out units 85 and 8S coupled, respectively, to the negative and positive-pulse terminals of unit 83, such units being provided to supply block-out voltages for suppressing the beam of tube 63 during transient periods which immediately precede and follow the tracing of each directive pattern. The circuits of units 85 and 86 are generally similar and correspond to that of a conventional keyed multivibrator. A suitable circuit arrangement is illustrated in Fig. 5 where it will be apparent that each block-out unit comprises a pair of triode vacuum tubes |30 and |3|. The anode of tube |36 is directly connected to the control electrode of tube |3I, while the anodeof tube |3| is coupled through condenser |35 to the control electrode of tube i3d. A diiferentiating circuit, comprising a series condenser |32 andshunt resistor |33, is provided in the input circuit of tube |30. A holding voltage obtained from a bleeder network including resistor |34 causes tube |3I normally to be biased to cutoff, while tube |30 is normally conductive. An input terminal g' is provided for the input circuit of the block-out arrangement to receive a control pulse, hereinafter described, which causes an output pulse to be obtained at an output terminal k. The output pulses developed in the transient block-out units 85, 86 are applied through amplifier 19 to the control electrode of tube 63 with' such polarity that the beam of the tube is suppressed during the aforesaid transient periods.

The direction nder has a further provision which distinguishes that portion of the line traced by the beam of cathode-ray tube 57 which is also traced by the beam of cathode-ray tube G3. This is accomplished through a further keying amplifier 93 which receives the succession of marker signals supplied by pulse detectors 69, 1B and applies such marker Ysignals to the control electrode of tube- 5l to bias the tube to `cutoff periodically at a frequency corresponding to the repetition rate of the applied signals. AAmplifier 93 is coupled to the negative-pulse` terminal of unit 'of the Voperation of those components which are similar in construction to identified portions of ,the aforementioned copending applications. The cnstruction an operating details of such comfponents may be obtained from the identified co- `pending applications. As'an aid in understanding the description which follows, direction aryrows fare provided on the conductors of Figs. l `and 2 toindicate the Vdirection of signal translation.

Assume for the moment that no signals `are "intercepted by antenna systemZ, 2| during its rotation through an azimuth of 360 degrees. For this condition, no output signal is derived in Vreceiver `25. However, this rotation of the antenna .system causes inductive-coupling devices Y -.36 .a-nd'3llto frequency-modulate the output sig- ,.nalsof oscillation generators 35 and 36, respectively. Preferably, units and 3l are so adjusted that the operating frequencies ofoscillation generators and 36 vary in response to Iantenna rotation, as indicated bycurves A and B, respectively, of Fig. 6a. It will be apparent .from these curves that the frequency of each generator variesin accordance with a sine function. of antenna rotation and that the modulation ,of Onegener'ator'has a QO-degree phase displace- 4menti with reference to the modulation of the other. Units 30' and ISI' modulate the output 4,signals Vof .oscillators 35 and respectively, Ain a `similar manner but at a frequency corresponding to four times that of the .antenna rotation. .At the same time,rmodulator S'I-phase-modulates the rsig'nal applied theretofrom oscillation generator L in .accordance .with .the rotation of .antenna r system 2 5, 2l, thereby to develop a lphase-modur,lated signal. This signal ycomprises the aforementioned comparative oscillations -having a `phasegrelaticn with reference to the oscillations produced 4in `oscillator 40 which -continuously varies at a rate corresponding .to twelve times `the antenna rotation. Also, .the carrier signal Afrom oscillationgenerator 4D is .amplitude-,modulatedinbalanced modulator 4I with a modulating .tsignahhaving a frequency .f5 to produce phasereference .sig-nal` components.

Theprincipal factors `inl determining Vthe value fof thewmodulating frequency f5 are represented Ain the frequency-spectrum of Fig. 7. In this g- .urafrequency component Yfo represents'the carlrier signal supplied by oscillation generator .40;

The `band of frequencies associated therewith, having the limiting frequenciesfo and fc4-Af, ,represents the bandof phase-modulation com- ,ponentsfproducedin modulator as antenna'sysrtemlz, .2| is brought from a condition of rest to `its maximum frequency fof rotation, for .one direction of antenna rotation. rIhe .frequency @band illustratedby-broken-line construction indicatesthe corresponding modulation components produced `under the sameconditions-but 4assuming the direction of antenna rotation ,to be Areversed. The frequency components indicated l-,Ju-i--fs :and .fo-,f5 represent the reference-signal components produced in. balanced modulator 4|. l 'Ihefrequencybands a. and bassociated with the kreferencesignal components .are considered herein after.` It will be noted from Fig 7 thatthe A*modulating frequency jfs is chosen so that the "developed reference-signal,components'fo-Hs and the earriersignal fo by equal and opposite increments of such magnitude that the band of phasemodulation components foinf is located therebetween.

Each of the aforedescribed signals produced in signal generator "'46 is amplied in amplifier '44 and applied to channel 41 forftranslation to the remote indicating arrangement. For the assumed operating condition, when there is no output signal derived in receiver 25, modulator `3 serves merely as an amplifier for the reference-signal components.

At' the line-tracing arrangementl (Fig. 2), the received signals are selectively amplified in unit '5I and delivered to the several filters associated therewith". Filters :'52 and 53 select the frequency-modulated signals having carrier frequencies f1 and 'fa respectively. For the assumed operating conditions, modulators 54 and 60 are biased nearly to cutoff and function merely as low-gain amplifiers and the selected signals are translated in the horizontaland vertical deflectionchannels of tube51 in a conventional manner. Detectors 55 and'l derive deflection signals therefrom for tube 51 which have sinusoidal amplitude variations and a time-phase displacement of degrees. "These signals cause the beam of the tube to trace a circular path in synchronism with the antenna rotation. Sincemodulators 54 and B are biased nearly to cutoff for the assumed conditions, the traced circular path has an exceedingly small radius and may appear on the screen of tube 57 as a dot. In like manner,

the frequency-modulated signals having carrier frequencies f3 and fr are utilized, respectively, in the horizontal and vertical deflection channels of tube 53 and cause the beam thereof to trace a circular path at a frequency corresponding to four times that ofthe antenna rotation. However, the circular path traced on the screen .of tube 63 has a large radius and appears vnear the edge of the screen. AThis results from the unidirectional potential applied to modulators 54 and 60 from unit 91 for the assumed conditions, i. e., with no signal output derived in detectors 8| and 82.

The reference-signal components o-s and fo-i-fs are separated by filters 64 and 65 and modulated in mixer 67 to produce a reference-.phase carrier signal corresponding to the second harmonic of the signal output from oscillation generator 40 in signal generator 46 and, therefore, also corresponding to the second harmonic ofthe carrier componentl of the received phase-modulated carrier signal. Also, the received phasemodulated carrier signal selected by filter 66 is doubled in frequency by multiplier 68. The outpu-t signals thus derived in units 61 and 58 are applied to detector where they are utilized .to derive desired marker signals for application vto cathode-ray tube 63.

While the oscillations of the original signals from oscillation generator ,4Q and modulator 31 continuously vary in phase at a rate corresponding to twelve times that of the antenna rotation, the oscillations of the corresponding signals derived in units 51 and 58, respectively, vary in phase at twice that rate, or at twenty-four times the antenna rotation, It will be seen, therefore, that the oscillations from units 51 and 68 have a predetermined phase relation, for exampleythe oscillations Will have substantially identical phase at intervals corresponding to every 15 degrees of --antennarotation Pulse-detector 69 of unit95-to Aunits 67 and 68 is effective to derive a single mark-er signal during each interval the applied oscillations have such predetermined phase relation. Hence, a succession of marker signals is 'l2 and those from frequency multiplier 68 to derive a single marker signal at each interval when such oscillations have substantially identical phase. Since the frequency of the oscillations from mixer 61 have been multiplied by three in multiplier l2, the succession of marker signals derived in this detector has a repetition frequency which is three times that ofthe marker signals derived in detector 69. In other words, the signals from detector 'l0 represent different predetermined positions of the antenna directive pattern having a 5-degree spacing.

Still another succession of marker signals is obtained from pulse detector 'il of unit 95. Inasmuch as the oscillations applied to this detector Ahave been multiplied in frequency fteen times,

the' derived signals individually represent different predetermined positions of the antenna directive pattern having a l-degree spacing.

The marker signals from detectors 89 and I0 are combined and applied to modulator 'i4 to modulate the second anode voltage of tube 63. Such modulation of the second anode voltage modulates the electron velocity of the beam of the tube, permitting the deiiecting elements to de- `ilect the beam radially at a rapid rate to produce major scale divisions on the screen. These scale divisions individually represent different prede'- termined positions of the antenna directive pattern having a, -degree spacing. A maximum tervals corresponding to every l5 degrees of antenna rotation by reason of the fact that the combined output signals of detectors S9 and 'IU -have peak values at such intervals. On the other hand, the output signal of detector 'iI is applied to the control electrode of tube 63 to energize the beam thereof periodically and produce minor scale divisions corresponding to every one degree of antenna rotation. Since the repetition frequencies of the signal outputs of units S9, 'l0 and are integrally related, unit 1| causes the beam of tube B3 to be energized at intervals when the beam is deflected radially to produce major scale divisions. The resulting scale provided on the screen is indicated in Fig. 2.

In brief, when no signals are intercepted during the rotation of antenna system 2i), 2| the beam of tube 5l is controlled to trace a circular `path of extremely small radius or a spot in synchronism with the antenna rotation. At the directive pattern. l Let it be assumed, now, that antenna systeml 2), 2| intercepts two radiant-energy signals in its rotation, one having an azimuth of de- .grees and the other an azimuth of 240 degrees. For this operating condition, an output signal radial deflection of the beam is obtained at inle is obtained from receiver 25 having amplitude variations which represent the antenna directive pattern with reference to the direction of reception, or bearing, of each received signal. The operation of signal generator 46 is substantially as described, except that the reference-signal components from unit 4| are now amplitude-modulated in unit 43 with the signal output of receiver 25. The output signal of this receiver is essentially a low-frequency signal having components corresponding to the frequency of antenna rotation (about 100 revolutions per minute) and harmonies thereof. The resulting bands of modulation components associated with each reference-signal component are designated a and b in n the frequen'cys'pect'rum of Fig. 7. t willbenoted that the modulating frequency f5 utilized in deriving the reference-signal components is chosen of such value that the bands of amplitude-modulation components a, b are so spaced in the frequency spectrum that the bands of phase-modulation components fo-i-Af and fri-Af produced Ain unit 3'| are located therebetween. This is a necessary frequency relationship to facilitate separation of the phase-modulation signal and the amplitude-modulated reference-signal components which are translated to the remote indicator over the single channel 41.

At the remote line-tracing arrangement (Fig. 2), detector 80 derives the amplitude-modulation components of the reference-signal component selected by lter 64. These modulation components represent the signal output of receiver 25 for the assumed operating condition and are utilized in modulators 54 and 60 to amplitude-modulatethe signals translated in the horizontal and vertical channels, respectively, of tube 57. The effect of this amplitude modulation is illustrated graphically by the curves of Fig. 8 where the full-line curve C is the frequency-response characteristic of detectors 55 and El for signals of a given intensity or constant amplitude. With reference to the circuit diagram of the detectors in Fig. 3, the characteristic of Fig. 8 is effective at the terminal a, and the frequencies fa and fb represent the peak-response frequencies of tuned circuits |93 and |04, respectively. For an applied signal 0f greater intensity, the frequency-response characteristic may be `as represented by broken-line curve C1. It will be seen that the slope of the response characteristic varies with the amplitude of the applied signal and, hence, the amplitude of the signal output from the detector varies with amplitude variations of the applied frequencymodulated signals. Thus, it will be apparent that modulation of the signals translated in the horizontal and vertical deilection channels of tube 51 with the signal output of detector modifies the deflection signals of the tube in accordance therewith. The modiied deiiection signals cause lthe beam of tube 51 to trace on the screen thereof the antenna directive pattern with reference to the direction of reception of each received signal. The resulting pattern is indicated in Fig. 2. A compass scale associated with the screen of the tube permits an approximate bearing indication of each received signal to be obtained.

Let it be further assumed that an accurate bear.. ing indication isY desired of the received signal having an azimuth of 30 degrees. Such indication may be obtained by controlling the `beam of tube 63 to trace at least a portionl of the antenna directive pattern with reference to the direction of reception of this particular signal. To accomplish this result, block-out control 9| is adjusted 17 to apply a control eiect to detectors 8| and 82 for rendering such detectors responsive only to the amplitude of a signal picked up within that fractional portion of the antenna rotation which corresponds to its rotation from west to east, assuming a clockwise direction of motion.

In considering the operation of block-out control 9| and square-wave limiter 92, reference is made to the curves of Figs. 6a, 6b and 6c. As previously indicated, curves A and B of Fig. 6a represent the frequency variations o the signals translated in the horizontal and vertical channels of tube 51 with the rotation of the antenna system. In Fig. 6b curves A1 and A2 represent the signal outputs obtained at terminals a and b, respectively, ofYr detector 55 in response to the signal translated thereby. Curves indicated B1 and B2 represent the corresponding output signals obtained at like terminals of detector 6|. These signals are applied to individual ones of the input terminals of block-out control 9| for selection by its switch arm |26. Unit 92, by symmetrically limiting the signal selected by switch arm |26, produces an alternating control potential having a, substantially rectangular wave form. Thus, as represented by the curves of Fig. 6c, the control arrangement may produce any of four control signals indicated by the curves A3, A4, Bs and B4 corresponding, respectively, to applied signals A1, A2, Bi and B2. It will be noted that in each case the alternating control signal has a fundamental frequency corresponding to that of the antenna rotation. Viewing the curves in the order A3, B4, A4 and B3, it will be seen that the four control signals available through the selective operation of the control arrangement have a relative phase displacement of 90 degrees. To make detectors 8|, 82 responsive to the signals picked up by the antenna system as it rotates from west to east, switch arm |26 of unit 9| is positioned, as indicated in the drawing, on terminal W-E which selects control signal B4 for application to terminals d of the detectors.

The operation of detectors 8|, 82 will now be Considered with reference to the curves of Figs. 9 and 10a through 10d. The .curve of Fig. 9 represents the envelope of the signal applied to the detectors from filters 64 and 65, respectively, for the assumed operating conditions. It will be apparent upon inspection that the direction-finder information (the signal output of receiver 25) is translated to the indicator arrangement of Fig. 2 as inward modulation of the reference-signal components fo-l-fe and ,fo-f5. Neglecting for a moment the control elect applied to the repeater circuits of the detectors from resistors |23, it will be seen that the signals derived in their load circuits by rectication of the applied amplitudemodulated reference-signal components are represented by the curve of Fig. 10a. Inasmuch as the detected signals have a negative polarity and repeaters are normally biased to cutoi, no output signals are obtained at terminals c of the detectors. However, by adjusting resistors |23, the peaks of the detected signals may be caused to have a positive polarity, as indicated by the curve of Fig. 10b, and Vthus may be translated through repeaters l 28 to output terminals c. With the selected control signal B4 of Fig. 10c applied from units 9| and 92 to terminals d of the detectors, their response is as shown by the curve of Fig. 10d. It will be seen that an output signal is obtained in response to the received signal having a bearing of 30 degrees, whereas the detectors are eiec- `tively nonresponsive to the signal having a bearing of 240 degrees. `This results from the fact that during the rotation of the antenna system from east to west the positive half-cycle of the control signal applied to terminals d of the detectors causes tubes |24 eiectively to short-circuit resistors |23 and thus remove the control effect applied therefrom to the repeater circuits of the detectors. The precise adjustment of resistors |23 is described hereinafter in connection with the direction-finder pattern produced on the screen of tube 63.

The output signals thus obtained from detectors 3| and 82 are combined and applied to unit 83 to be formed into a control pulse of substantially rectangular wave form. The negative control pulse produced at terminal g of unit 83 is represented on an expanded time scale in Fig. 11a. This pulse is diierentiated in the input circuit of block-out device 85, thereby to derive negative and positive pulses from the leading and trailing edges, respectively, as shown in Fig. 11b. The derived negative pulse biases tube |30 of the multivibrator arrangement 85 to cutoff, thereby rendering tube |3| conductive. This tube conducts for one time cycle, determined by the time constant of condenser |35 and resistor |33, to produce at the output terminal k of the block-out arrangement a pulse indicated by the curve of Fig. 11o having a predetermined duration. This block-out pulse is applied through amplifier 'I9 to the control electrode of tube 63 to suppress the beam thereof during the transient period which immediately precedes the tracing of a direction-finder pattern.

The positive control pulse from terminal e of unit 83 is applied to unit 91 and removes the above-mentioned unidirectional potential from modulators 54 and 68 in a manner similar to the described operation of tubes |24 which removes a similar unidirectional potential from the repeater circuits of detectors 8| and 82. The positive control pulse also energizes keying amplifier 84, thereby to translate the combined signal output from detectors 8| and 32 through amplifier 84 to modulators 54 and 69. These modulators operate in a manner similar to that described in connection with units 54 and 60 to control the beam 0f the cathode-ray tube 63 to trace a direction-iinder pattern in accordance with the output signal of detectors 8| and 82. The positive control pulse of unit 83 also energizes the beamdisplacement arrangement through its control of oscillator 88. Winding 8l of this arrangement displaces the beam of tube 63 angularly at a high rate during the interval when the beam is controlled to trace a direction-linder pattern. Control pulses from rectifier 96 energize the beam at each instant when the beam has its maximum angular displacement, thereby to produce intersecting patterns on the screen of tube 63 whose intersections with reference to the scale divisions on the screen thereof sharply determine the direction of reception or bearing of the particular signal. Accurate bearing indications are readily obtained by properly adjusting the taps on resistors |23 associated with the circuits of detectors 8| and 82. The adjustments should be such that the response of the detectors is limited to that portion of the signal output of receiver 25 during the selected fractional rotation of the antenna system which produces patterns on the tube 63 intersecting at an angle of between 45 and degrees. In general, it will be satisfactory to adjust the control resistors |23 so as to cause the detectors to respond to that part of the signal altaar 19 11.9 output rfrom receiver Y25 which corresponds to the top twenty-live per cent of the antenna directive pattern.

When the selected portion of the antenna, directive pattern has been traced, transient blockout 85 produces a block-out pulse for again suppressing the .beam of tube S3. .The operation of this unit is clearly represented by the curves of Figs. 12a to 12o, inclusive, and is generally similar to that already described .in connection with unit 85.

During the intervals when the beam of tube 63 is controlled to trace a direction-finder pattern, unit 53 through. its association with keying amplier 18 and oscillator 15 disables the marker system. Further, Yunit 83 blocks keying amplifier .'13 for such intervals so that the portion of the direction-finder pattern which is traced simultaneously by tubes 51 and 63 appears on the former in a full-line construction, whereas amplifier 9.3 causes all other portions of the pattern on tube 51 to have a broken-line construction. This feature facilitates correlating the patterns appearing on thescreens of the two tubes. In the instant case, for example, it will be apparent upon inspection that the screen of the tube 63 represents the first Vquadrant of the screen of tube 51. Hence, the scale divisions on screen 63 for the assumed conditions represent the rst 90 degrees of antenna rotation.

In brief, it will be seen that the beam of tube 51 isrcontrolled to trace the antenna directive lpattern with reference to the direction of reception of each signal intercepted by antenna system 2Q, 2| during its rotation. The beam of tube 53, however, is normally controlled to establish vscale divisions on its screen except for that predetermined fractional portion of the antenna rotation when the antenna intercepts the particular signal whose bearing is to be determined accurately. During such predetermined fractional portion of the antenna rotation, the beam of tube 63 traces a selected portion of the antenna directive pattern with reference to the direction of reception of this particular signal and during such intervals the marker system is disabled. However, the persistence of the screen causes the directive pattern to be traced with reference to scale divisions previously established on the screen. It will be apparent that tube 63 produces an expanded or Vernier representation of the selected portion of the antenna directive pattern and that this expanded representation permits extremely accurate bearing indications to be obtained.

If an accurate bearing indication should be desired of the signal having a 24U-degree azimuth, it is only necessary to adjust switch arm |26 of unit 9| to the position indicated E-W. This position of the control switch applies control signal B3 of Fig. 6c to detectors 8|, 82, rendering the detectors responsive only to the amplitude variations of the desired signal. Again, the taps on resistors |23 of the detectors are to be adjusted to produce sharply intersecting patterns on the screen of tube153.' The bearing indication that would be obtainedV is as represented by the curves `of Fig. 13. It will be apparent that for this condition the scale on tube 63 represents the rotation of the antenna system from 180 to 270 degrees.V

In the described embodiment, units 9| and 92 produce a control effect capableof suppressing the operation of detectors 8 82.for approximatelylSOdegrees of antenna rotation. While such an arrangement is satisfactory for many installations, it may be desirable for other applications to suppress the operation of the detectors for a longer portion of the antenna rotation. For example, with the beam of tube 53 rotating at four times the antenna rotation, it may be desirable to have the detectors responsive only to the amplitudes of signals picked up Within a predetermined quadrant of antenna rotation. Many different arrangements may be utilized to provide this operation, a simple one being illustrated in Fig. 14. This arrangement comprises a two-Section switch which has four terminals |55 (only two of which appear in the drawings) having a circular arrangement in an insulating mounting strip |5|. The terminals are engaged on one side of the mounting strip by a brush |52 secured to a shaft |53 which may be rotated by means of a control dial |54. The terminals are engaged on the opposite side of the mounting strip by a second brush |55 carried by a bushing |56 rotatable about shaft |53. A gear |51 is also secured to bushing |56 and is engaged by a second gear |58 carried by a stub shaft |59 rotatably supported in a mounting plate |60. A control knob |6| also secured to shaft |59 permits brush |55 to be positio-ned upon a selected one oi terminals |50. Brushes |52 and |55 are suitably connected to an output terminal |611 of the switch arrangement by way of leads |62 and |63.

The described control switch may be utilized in the arrangement of Fig. 2 in place of units 9| and 92. However, in making the substitution, squarewave limiters 1| and a clipper |12V are to be coupled to the control switch, as indicated in Fig. l5 where the switch is designated schematically at |10. More particularly, unit |1| includes four square-wave limiting stages individually coupled to one of the input terminals |50 of the switch and clipper |12 is coupled to the output terminal |64 of the switch. The'input terminals of unit |1| are to be individually connected to one output terminal a or b of detectors 55 and 6|; the output terminal of clipper |12 is to be connected to control-pulse input terminals d of detectors 8| and 82; and control tubes |24 of detectors 8| and 82 are to be normally conductive, short-circuiting the associated voltage divider |23.

The operation of the modiiied control arrangement, When coupled to the line-tracing arrangement of Fig. 2 as described above, is shown by the curves of Figs. 16a to 16d, inclusive. In Fig. 16a, for example, the operation indicated results when one of brushes |52, |55 is positioned on that switch terminal which is connected with output terminal b of detector 55, ,while the other is positioned on that switch terminal which connects with terminal bv of detector 6|. With the brushesl in the positions indicated, the switch combines the signal outputs Yobtained from the identied terminals of detectors 55 and 6|, after these signals have been shaped in unit |1| Yto have the wave forms represented, respectively, by curves A2 and B2', and supplies the combined signal to clipper |712. The signal thus applied to clipper |12 has the Wave form of curve D1 and by peak-limiting in unit |12, a negative control pulse is derived for application to terminals dof detectors 8| and 82. It'will be noted from curve D1 that this control signal of 'negative polarity occurs during the iirst quarter of the antenna rotation and When applied to'detectors 8l and 82, modied to have tubes |24 normally conductive, causes the detectors to respond to the amplitudes of signals picked up during this predetermined fractional portion of the antenna rotation. Corresponding curves of Figs. 1Gb, 16e and 16d show the output signals selected from detectors 55 and 6| by selectively positioning brushes |52 and |55 and the resulting negative control pulses derived in unit |12. It will be apparent that such control effects may be utilized to render the detectors 8|, 82 responsive to any of the remaining quadrants of antenna rotation. By positioning both brushes on the same terminal of the switch arrangement, control effects may be obtained from unit |12 having wave forms represented by the curves of Fig. 6c. Thus, the described switching arrangement is flexible and affords a wideV control over the response of detectors 8|, 82.

The modified control arrangement, including a switch of the type illustrated in Fig. 14, so controls detectors 8| and 82 that these detectors comprise means responsive only to the amplitudes of signals picked up within a predetermined quarter of the antenna azimuthal rotation for shifting the line traced by the beam of tube 63. In other words, this means is responsive to a fractional portion of the antenna rotation, which fraction has a value not substantially greater than the reciprocal of the integer relating the rotation of the antenna and the rotation of the beam of tube 63.

While in a preferred embodiment of the inventionV antenna system 20, 2| is rotated through an azimuth of 366 degrees7 it will be apparent that, if desired, the antenna may be oscillated through a lesser azimuth. Also, the beam of cathode-ray device 3 need not necessarily be rotated at four times the frequency of the antenna rotation. For example, it may be desirable in certain installations to rotate the beam of this tube at a reduced speed.

Further, it will be understood that a direction finder in accordance with the invention may utilize a single cathode-ray line-tracing device. However, to obtain all of the advantages of the invention with such an arrangement, the beam of such device may be rotated in synchronism with the antenna system for a first interval in order to obtain a directive pattern representing the bearing of each signal intercepted during the rotation of the antenna system. Then, to derive an accurate bearing indication of a particular signal, the device may be operated for another predetermined interval in accordance with the described operation of tube 63.

It will also be understood that in place of antennasystem 2d, 2l a pick-up system may be utilized which is capable of receiving periodic sound or light signals and a phrase a direction finder for determining the direction of reception of a particular radiant-energy signal is intended to include such other applications. Additionally, the signal-translating channel l may, if desired, be a radio link instead of a conventional telephone chanel as described.

Whiie there has been described what is at present considered to be the preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modiications may be made therein without departing from the invention, and it is, therefore, aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A direction finder for determining the direction of reception of a particular radiant-energy signal comprising, a pick-up system having a directive pattern, means for controlling said pickup system to cause said directive pattern to rotate through a predetermined azimuth, line-tracing means, means for controlling said line-tracing means to trace a line at a frequency which is related to the frequency of rotation of said directive pattern by an integer greater than unity, and means responsive only to the amplitudes of signals picked up Within a predetermined fractional portion of said azimuthal rotation for shifting the line traced by said line-tracing means in accordance therewith to trace at least a portion of said directive pattern.

2V. A direction finder for determining the direction of reception of a particular radiant-energy signal comprising, a pick-up system having a directive pattern, means for controlling said pickup system to cause said directive pattern to rotate through a predetermined azimuth, line-tracing means, means for controlling said line-tracing means to trace a line at a frequency which is related to the frequency of rotation of said directive pattern by an integer greater than unity, and means responsive only to the amplitudes o fhsignals picked up within a predetermined fractional portion of said azimuthal rotation which has a value not substantially greater than the reciprocal of said integer for shifting the line traced by said line-tracing means in accordance therewith to trace at least a portion of said directive pattern.

3. A direction finder for determining the direction of reception of a particular radiant-energy signal comprising, a pick-up system having a directive pattern, means for controlling said pickup system to cause said directive pattern to rotate through a predetermined azimuth, a cathoderay line-tracing device, means for controlling the cathode-ray beam of said device to trace a circular path at a frequency which is related to the frequency of rotation of said directive pattern by an integer greater than unity, and means responsive only to the amplitudes of signals picked up within a predetermined fractional portion of said azimuthal rotation for modulating the radius of said circular path in accordance therewith to trace at least a portion of said directive pattern. s

4. A direction finder for determining the direction of reception of a particular radiant-energy signal comprising, a pick-up system having a directive pattern, means for controlling said pickup system to cause said directive pattern to rotate through a predetermined azimuth, line-tracing means, means for controlling said line-tracing means to trace a line at a frequency which is related to the frequency of rotation of said directive pattern by an integer greater than unity, means for deriving a control effect during a predetermined fractional portion of said azimuthal rotation, means responsive to the amplitudes of signals picked up by said system during said rotation for shifting the line traced by said linetracing means in accordance therewith, and means for utilizing said control effect to cause the line traced by asid line-tracing means to be shifted only in response to the amplitudes of signals picked up within said fractional portion of said rotation, thereby to trace at least a portion of said directive pattern.

5. A direction nder for determining the direction of reception of a particular radiantenergy signal comprising, a pick-up system having a directive pattern, means for controlling said pick-up system to cause said directive pattern to rotate through a predetermined azimuth, line-tracing means, means for controlling said line-tracing means to trace a line at a frequency which is related to the frequency of rotation of said directive pattern by an integer greater than unity, means for deriving a control effect in response to a predetermined fractional portion of said azimuthal rotation, means responsive to the amplitudes of signals picked up by said system during said rotation for shifting the line traced by said line-tracing means in accordance therewith, and means for utilizing said control effect to cause the line traced by said line-tracing means to be shifted only in response to the amplitudes of signals picked up within said fractional portion of said rotation, thereby to trace at least a portion of said directive pattern.

6. A direction finder for determining the direction of reception o-f a particular radiantenergy signal comprising, a pick-up system having a directive pattern, means for controlling said pick-up system to cause said directive pattern to rotate through a predetermined azimuth, line-tracing means, means for controlling said line-tracing means to trace a line at a frequency which is related to the frequency of rotation of said directive pattern by an integer greater than unity, means for deriving a control effect during a predetermined fractional portion of said azimuthal rotation, means responsive to the ampliltudes of signals picked up by said system during said rotation for shifting the line traced by said line-tracing means in accordance therewith, and means for applying said control effect to said lastnamed means to cause the line traced by said line-tracing means to be shifted only in response to the amplitudes of signals picked up Within said fractional portion of said rotation, thereby to trace at least a portion of said directive pattern.

7. A direction nder for determining the direction of reception of a particular radiantenergy signal comprising, a pick-up system having a directive pattern, means for controlling said pick-up system to cause said directive pattern to rotate through a predetermined azimuth, line-tracing means, means for controlling said line-tracing means to trace a line at a frequency which is related to the frequency of rotation of said directive pattern by an integer greater than unity, means for deriving an alternating control potential in synchronism with said rotation, means responsive to the amplitudes of signals picked up by said system during said rotation for shifting the line traced by said line-tracing means in accordance therewith, and means for utilizing a predetermined fractional portion of said control potential to cause the line traced by said line-tracing means to be shifted only in response to t-he amplitude of a signal picked up within a corresponding fractional portion of said azi- -muthal rotation, thereby to trace at least a portion of said directive pattern.

4-8. A direction finder for determining the direction of reception of a particular radiantenergy signal comprising, a pick-up system having a directive pattern, means for controlling said pick-up system to cause said directive pattern to rotate through a predetermined azimuth, line-tracing means, means for controlling said line-tracing means -to-trace1a Vline at a frequency which is related to the frequency of rotation of said directive pattern by an integer lgreater than unity, means responsive only to the amplitude of a signal picked up Within a predetermined fractional portion of said azimuthal rotation for shifting ,they line traced by said line-tracing means in accordance therewith to trace a selected portion of said directive pattern, and means for cyclically displacing the line traced by said linetracing means at a frequency which is high with reference to the frequency at which said line is traced to produce intersecting lines sharply indicative of the direction of reception of said signal.

9. A direction finder for determining the direction of reception of a particular radiantenergy signal comprising, a pick-up system having a directive pattern, means for controlling said pick-up system to cause said directive pattern to rotate through aipredetermined azimuth, line-tracing means, means for controlling said line-tracing means to trace a line at a frequency which is related to the frequency of rotation of said directive pattern by an integer greater than unity, means responsive only to the amplitude of a signal picked up within a predetermined fractional portion of said azimuthal rotation for l shifting the line traced by said line-tracing means in accordance therewith to trace at least a portion of said directive pattern, means for limiting the response of said last-named means Within said fractional portion of said rotation to cause said line-tracing means to trace a selected portion of said directive pattern, and means for cyclically displacing the line traced by said line-tracingA means at a frequency which is high With reference to the frequency at which said line is traced to produce intersecting lines sharply indicative of the direction of reception of said signal.

l0. A direction finder for determining the direction of reception of a particular radiant-energy signal comprising, a pick-up system having a directive pattern, means for controlling said pick-up system to cause said directive pattern to rotate through a predetermined azimuth, linetracing means, means for controlling said linetracing means to trace a line at a frequency which is related to the frequency of rotation of said directive pattern by an integer greater than unity, detector means responsive only to the amplitude of a signal picked upv Within a predetermined fractional portion of said azimuthal rotation for shifting the line traced by said line-tracing means in accordance therewith to trace at least a portion of said directive pattern, means for applying a control potential to said detector means to limit the response of said detector means within said fractional portion of said ro- Y'piola-up system to cause said directive pattern to rotate through a predetermined azimuth, linetracing means, means for controlling said linetracing .means to .trace a rline at a frequency :which :is related to the frequency of rotation ,of ,said :directive pattern byian integer greater than unity, detector means responsive only to the amplitude of a signal picked kup within a ,predetermined 'fractional .portion iof said azimuthal .rotation for shifting the line traced by said linetracing means in accordance therewith to trace at least a portion of said directive pattern, means for applying a control bias to said detector means to limit the response of said detector means within said fractional portion of said rotation to cause said line-tracing means to trace a selected portion of said directive pattern, and means for cyclically displacing the line traced by said linetracing means at a frequency which is high with reference to the frequency at which said line is traced to produce intersecting lines sharply indin cative of the direction of reception of said signal.

12. A direction finder for determining the direction of reception of a particular radiant-energy signal comprising, a pick-up system having a directive pattern, means for controlling said pick-up system to cause said directive pattern to rotate through a predetermined azimuth, linetracing means, means for controlling said line tracing means to trace a line at a frequency which is related to the frequency of rotation of said directive pattern by an integer greater than unity, means for deriving a succession of marker signals individually representing different predetermined positions of said directive pattern, means for applying said marker signals to said line-tracing means to provide scale divisions corresponding to said predetermined positions, means responsive only to the amplitude of a signal picked up within a predetermined fractional portion of said azimuthal rotation for shifting the line traced by said line-tracing means in accordance therewith to trace at least a portion of said directive pattern with reference to said scale divisions, and means for rendering said line-tracing means unresponsive to said marker signals only during intervalsyvhen the line traced thereby is shifted to trace said directive pattern.

13. A direction finder for determining the direction of reception of a particular radiant-energy signal comprising, a pick-up system having a directive pattern, means for controlling said pick-up system to cause said directive pattern to rotate through a predetermined azimuth, linetracing means, means for controlling said linetracing means to trace a line at a frequency which is related to the frequency of rotation of said directive pattern by an integer greater than unity, means for deriving a succession of marker signals individually representing different predetermined positions of said directive pattern, means for applying said marker signals to said line-tracing'neans to provide scale divisions corresponding to said predetermined positions, means responsive only to the amplitude of a signal picked up within a predetermined fractional portion of said azimuthal rotation for shifting the line traced by said line-tracing means in accordance therewith to trace at least a portion of said directive pattern with reference to said scale divisions, and means responsive to said lastnarned means for rendering said line-tracing means unresponsive to said marker signals during intervals when the line traced thereby is shifted to trace said directive pattern.

14. A direction-finder for determining the direction of reception of a particular radiant-energy signal comprising, a pick-up system having a directive pattern, means for controlling said pick-up system to cause said directive pattern to rotate through a predetermined azimuth, linetracing means, means for controlling said linetracing means to trace a line at a frequency which is related to the frequency of rotation of said directive pattern by an integer greater than unity, means for deriving a succession of marker signals individually representing different predetermined positions of said directive pattern, means for applying said marker signals to said line-tracing means to provide scale divisions corresponding to said predetermined positions, means responsive only to the amplitude of a signal picked up within a predetermined fractional portion of said azimuthal rotation for shifting the line traced by said line-tracing means in accordance therewith to trace at least a portion of said directive pattern with reference to said scale divisions, means for cyclically displacing the line traced by said line-tracing means at a frequency which is high with reference to the frequency at which said line is traced to produce intersecting lines sharply indicative of the direction of reception of said signal, means for deriving a control effect from said signal picked up within said fractional portion of said rotation, and means for utilizing said control eiect to energize said line displacing means and to render said line-tracing means unresponsive to said marker signals during intervals when the line traced thereby is shifted to trace said directive pattern.

15. A direction finder for determining the direction of reception of a particular radiant-energy signal comprising, a pick-up system having a directive pattern, means for controlling said pick-up system to cause said directive pattern to rotate through a predetermined azimuth, linetracing means, means for controlling said linetracing means to trace o, first line in synchronism with the rotation of said directive pattern, means for controlling said line-tracing means to trace a second line at a frequency which is related to the frequency' of rotation of said directive pattern by an integer greater than unity, means responsive to the amplitudes of signals picked up during said azimuthal rotation for shifting said rst line traced by said line-tracing means in accordance therewith to trace said directive pattern with reference to thedirection of reception of each of said signals,`and means responsive only to the amplitude. of a signal picked up within a predetermined fractional portion of said azimuthal rotation for shifting said second line traced by said line-tracing means in accordance therewith to trace at least a portion of said directive pattern with reference to the direction of reception of said signal.

16. A direction finder for determining the direction of reception of a particular radiant-energy signal comprising, a, pick-up system having a directive pattern, means for controlling said pick-up system to cause said directive pattern to rotate through a predetermined azimuth, linetracing means including a first and a second linetracing device, means for controlling said first device to trace a line in synchronism with the rotation of said directive pattern, means for controlling said second device to trace a line at a frequency which is related to the frequency of rotation of said directive pattern by an integer greater than unity, means responsive to the am* plitudes of signals picked up during said azimuthal rotation for shifting the line traced by said rst device in accordance therewith to trace said directive pattern with reference to the direction of reception of each of said signals, and means responsive only to the amplitude of a signal picked up within a predetermined fractional portion of said azimuthal rotation for shifting the line traced by said second device in accordance therewith to trace at least a portion of said directive pattern with reference to the direction of reception of said signal.

17. A direction finder for determining the direction of reception of a particular radiant-energy signal comprising, a pick-up system having a directive pattern, means for controlling said pick-up system to cause said directive pattern to rotate through a predetermined azimuth, cathode-ray line-tracing means including a rst and a second line-tracing device, means for controlling the cathode-ray beam of said first device to trace a circular path in synchronism with the rotation of said directive pattern, means for controlling the cathode-ray beam of said second device to trace a circular path at a frequency which is related to the frequency of rotation of said directive pattern by an integer greater than unity, means responsive to the amplitudes of signals picked up during said azimuthal rotation for modulating the radius of the circular path traced by said rst device in accordance therewith to trace said directive pattern with reference to the direction of reception of each of said signals, and means responsive only to the amplitude of a signal picked up within a predetermined fractional portion of said azimuthal rotation for modulating the radius of the circular path traced by said second device in accordance therewith to trace at least a portion of said directive pattern With reference to the direction of reception of said signal.

-18. A direction finder for determining the direction of reception of a particular radiant-energy signal comprising, a pick-up system having a directive pattern, means for controlling said pickup system to cause said directive pattern to rotate through a predetermined azimuth, line-tracing means, means for controlling said line-tracing means to trace a first line in synchronism with the rotation of said directive pattern, means for controlling said line-tracing means to trace a second line at a frequency which is related to the frequency of rotation of said directive pattern by an integer greater than unity, means responsive to the amplitudes of signals picked up during said azimuthal rotation for shifting said first line traced by said line-tracing means in accordance therewith to trace said directive pattern with reference to the direction of reception of each of said signals, means responsive only to the amplitude of a signal picked up Within a predetermined fractional portion of said azimuthal rotation for shifting said second line traced by said line-tracing means in accordance therewith to trace at least a portion of said directive pattern with reference to the direction of reception of said signal, and means for distinguishing that portion of the pattern traced by shifting said rst line which is also traced by shifting said second line.

19. A direction nder for determining the direction of reception of a particular radiant-energy signal comprising, a pick-up system having a, directive pattern, means for controlling said pickup system to cause said directive pattern to rotate through a predetermined azimuth, cathoderay line-tracing means including a'rst and a second line-tracing device, means for controlling the cathode-ray beam of said rst device to trace a circular path in synchronism with the rotation of said directive pattern, means for controlling the cathode-ray beam of said second device to trace a circular path at a frequency which is re.- lated to the frequency of rotation of said directive pattern by an integer greater than unity, means responsive to the amplitudes of signals picked up during said azimuthal rotation for modulating the radius of the circular path traced -by said first device in accordance therewith to trace said directive pattern with reference to the direction of reception of each of said signals, means responsive only to the amplitude of a signal picked up Within a predetermined fractional portion of said azimuthal rotation for modulating the radius of the circular path traced by said second device in accordance therewith to trace at least a portion of said directive pattern with reference to the direction of reception of said signal, means for deriving a control eiect from said signal picked up within said fractional portion of said rotation, and means for applying said control effect to said first device to distinguish that portion of the line traced by said first device which is also traced by said second device.

BERNARD D. LOUGI-ILIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Luck et al. V June 21, 1938 Oct. 21, 1947. A. M. COHAN 2,429,548

l PROPELLENT FUEL CARTRIDGE l Fiied sept. 2o, 194s INVENTOR ATTORNEY 

